As election season in the U.S. reaches its final week and Democratic presidential candidate Hillary Clinton faces yet another resurgence of her email investigation, her aide, Huma Abedin, has also been receiving more attention.

Abedin, described by Clinton as her "second daughter", separated from her husband, Anthony Weiner, earlier this year.

Weiner is the subject of an investigation into allegations that he sent lewd pictures and sexual messages to a 15-year-old girl. The former congressman has a colorful history of sexting scandals, throughout most of which Abedin had stood by him.

But most recently, another batch of Clinton emails sent from a private server were found on a computer shared by Weiner and Abedin. The emails brought Clinton back under the eye of the FBI just a week before the election, but also tied her and Abedin back to Weiner, her estranged husband.

Abedin has been by Hillary Clinton's side since she was a 19-year-old intern to the then-first lady in the early 1990s, while she finished her undergraduate degree at George Washington University.

Since then, she has been Hillary Clinton's aide, traveling chief of staff for her 2008 presidential campaign, deputy chief of staff to Clinton as secretary of state, and vice chairwoman of the current presidential campaign.

During the past two decades, Abedin has been seen by Clinton's side, maintaining the job of "aide" or "bodywoman" normally held by younger staffers. She briefly took a break from Clinton in 2013 to stand beside her husband as he bid for mayor of New York, but as that campaign was shattered by yet another scandal involving Weiner sending inappropriate messages to women, Abedin seamlessly resumed working for Clinton.

Some of the recently leaked emails would indicate that Abedin is moving toward being a "surrogate" for Clinton, pre-screening all staff on the current campaign as well as holding meetings such as a 45-minute one-on-one with New York Mayor Bill de Blasio when Clinton was running late to meet him.

Huma Abedin, a longtime aide to Hillary Rodham Clinton, speaks to the media after testifying at a closed-door hearing of the House Benghazi Committee, on Capitol Hill, Oct. 16, 2015 in Washington.

Under scrutiny

But Clinton and Abedin have been so close, particularly during their time at the State Department, that Abedin's role has come under scrutiny. Congress is looking into whether she received special treatment while she was deputy chief of staff to the secretary of state, particularly because of reports suggesting that she was being paid from Clinton's personal payroll as well as by private consulting firm Teneo.

After this weekend's revelation about Clinton's emails found on a computer shared by Abedin and Weiner, some have called for her to step away from the campaign.

“We of course stand by her,” Clinton campaign Chairman John Podesta told the New York Times on Saturday, when asked whether Abedin would step down.